Electromagnetic actuator



Aug. 5, 1969 R. w. REITHERMAN 3,460,001

ELECTROMAGNETIC ACTUATOR Filed April 15, 1967 INVENTOR RALPH w REITHERMAN 444% BY MM r/ww ATTORNEYS.

United States Patent 3,460,001 ELECTROMAGNETIC ACTUATOR Ralph W. Reitherman, Lake Villa, 11]., assignor to Skill- Di, Inc., a corporation of Illinois Filed Apr. 13, 1967, Ser. No. 630,767 Int. Cl. H01h 47/00, 3/28; 1101f 7/00 US. Cl. 317-1555 10 Claims ABSTRACT OF THE DISCLOSURE A multiple function electromagnetic actuator having a plurality of solenoids with a magnetic housing which has sufficient cross-sectional area to avoid saturation with energization of the one solenoid, but which area is less than that required if the solenoids were housed individually.

This invention relates to an electromagnetic actuator.

It is sometimes desirable to provide for electromagnetic actuation of small mechanical devices. If plural devices to be actuated are closely spaced, it may be difficult to provide electromagnetic actuation with suflicient operating force to be elfective, as the size of each coil and the cross-section of the iron core structure are limited. This restriction on operating force has prevented use of such actuators in situations where size is critical.

In accordance with the invention, plural electromagnetic actuators have a common magnetic path, as by being housed in the common enclosure of magnetic material. Where less than all of the actuators are energized at any time, the magnetic housing has sufiicient area to avoid saturation, but is smaller than that which would be required if each coil was provided with its own magnetic path. This sharing of magnetic material reduces the total volume and weight of the magnetic path and permits closer spacing of the actuators than would otherwise be possible.

One feature of the invention is that it enables use of selectively operable electromagnetic actuators for the operation of closely spaced mechanical devices.

Another feature of the invention is that multiple coil eletromagnetic actuators may be assembled with less core material than is required for separate actuators of the same mechanical capacity, resulting in a reduced size, weight and cost.

Further features and advantages of the invention will readily be apparent from the following specification and from the drawings, in which:

FIGURE 1 is a side view of a multiple function electromagnetic actuator embodying the invention, in combination with a push button UHF television tuner;

FIGURE 2 is an end view thereof with a portion of the electromagnetic actuator in section; and

FIGURE 3 is a section taken generally along line 3-3 of FIGURE 1, with an electrical circuit for operating the actuators illustrated schematically.

While an illustrative embodiment of the invention is shown in the drawings and will be described in detail herein, the invention is susceptible of embodiment in many different forms and it should be understood that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.

Television receivers, which are now required by Federal Communications Commission regulations to incorporate UHF tuners, often have a multichannel push button tuning mechanism to permit accurate selection of programmed UHF channels without resort to a fine tuning adjustment each time the UHF channel setting is changed. The structure of the tuner itself and of the push button 3,460,001 Patented Aug. 5, 1969 tuning mechanism forms no part of the present invention and is not disclosed in detail herein. Where a television receiver is provided with remote control, it is desirable that this remote control be capable of selecting the UHF channels for which the push button mechanism is programmed. This can readily be accomplished if some means are available for mechanically actuating the push buttons. The multiple function electromagnetic actuator of this invention serves this purpose.

Turning now to the drawings, the UHF push button tuner 10 is provided with five channel selection push buttons 11 arranged in a side-by-side relationship and mounted on push rods 12 which extend into the tuner 10. Depression of a push button will set the circuit tuning elements (not shown) of the tuner for the channel desired. UHF television tuners, as other components of television receivers, are designed to occupy as small a space as possible, to reduce the overall size of the television receiver and to minimize weight, material cost, and the like. A typical UHF tuner is less than three inches long, two and one half inches wide and one and one-half inches deep. A row of five push buttons on such tuner might have a center-to-center push rod spacing of the order of one-half inch. If the coils of the electromagnetic actuators are aligned with the push rods, as is desirable from a mechanical standpoint, the coils for each actuator and the iron associated therewith must be quite small.

The multiple electromagnetic actuator 15 is mounted on arms 16 extending from the tuner housing. Five coils, 17a-17e, each have an armature, 18a'18e, movable axially therein and aligned with the push rod 12 of the corresponding push button 11. Each armature is connected with the corresponding push rod through a suitable link 19.

The coils 17 are generally oval in cross-section (FIG- URE 3) and have the major axis at right angles to the line of the push rods 12. This provides a coil window or opening 20 of maximum size while minimizing the space requirements of the coils in the direction of the line of push rods. In the deactuated condition, each armature 18 is at least partially removed from the associated coil by virtue of the connection with the push rod, which has a return spring (not shown). Upon energization of a coil, the armature is drawn to the left as viewed in FIGURES 1 and 2, pulling the associated push rod 12 with it and actuating tuner 10.

In accordance with the invention, the solenoids 1711- 17e have a common magnetic structure which provides a return path for the flux set up by energization of each coil. This common magnetic structure is a housing of soft iron having four side walls 21, 22, 23 and 24, and end walls 25 and 26 which form an enclosure for the coils. The coils are fixed within a housing by a suitable insulating material 27, as an epoxy resin, in which they are embedded. As seen in FIGURE 2', the embedding material does not fill the space between the coil and wall 23, aligned with the coil opening. Wall 24 has an opening 24a therein aligned with the coil window 20 to accommodate the armature 18. Similar openings are provided in plate 23 to allow the armature to move a short distance outwardly beyond the inner wall surface upon actuation. This eliminates the noise which results if the armature strike a solid wall. The push button mechanism has sufiicient resilience or give to allow a short overtravel although the steady state position of the armature of an energize solenoid is inside the housing. The absence of magnetic housing material in line with the window 20 of the coil reduces the retarding effect on the armature of retained magnetism in the housing when the coil is deenergized.

The force exerted by a solenoid is determined by the strength of the magnetic field, or the total flux which is established upon energization of the coil. The total flux resulting from energization of one coil is dependent on the electromotive force of the coil, i.e., the number of turns in the coil and the current which flows through it, and the reluctance of the magnetic path through which the flux passes. The reluctance is a function of the path length and the cross-sectional area at right angles to the direction of the flux. The relationship between flux and the electromagnetic force is relatively linear so long as saturation of the magnetic material through which the flux passes is not approached. On the other hand, if the magnetic material is saturated, the flux is limited and an effective limit is placed on the physical force exerted by the armature. If each coil 17 had sufficient iron surrounding it to provide an adequate path for the flux without reaching saturation, the coil and its associated magnetic structure would require so much space that the electromagnetic actuator assembly could not readily be incorporated in the UHF push button tuner. Furthermore, the added iron would increase the weight and cost of the actuator. With the coils in a common housing of magnetic material, however, the housing provides adequate iron cross-section to enable establishment of the necessary magnetic field for each coil without reaching saturation. As only one coil is energized at a time, the total iron which is required is substantially less than that if separate magnetic structures were utilized. In effect, each coil, when energized, borrows from its neighbor (and also makes use of the end plates 25 and 26) to provide a path for the flux.

FIGURE 3 illustrates schematically a circuit for energizing the solenoid coils in a remote control system for a television receiver. An antenna 30 receives a signal from a remote source and detector 31 derives signals which control actuation of individual channel switches 32(1-328, one at a time. The coils 17a-17e each have two terminals, one connected to a common or ground 32 and the other connected through a channel switch to a source of operating potential, as battery 34. The remote control system has suflicient channels to provide for selective actuation of each of the switches, in turn selectively energizing each of the solenoid coils and adjusting the tuner to a programmed station.

I claim:

1. A multiple solenoid structure comprising: a housing composed of parts forming a tube of rectangular crosssection and at least partially of magnetic material, a plurality of openings equally spaced apart in one Wall of the tube, a plurality of solenoid armatures reciprocable in said openings, and a plurality of solenoid windings supported in said housing, each surrounding and forming a slot for an armature and each winding being energizable from a source to establish a magnetic flux which extends into and magnetizes the armature associated therewith and the housing between the openings on each side thereof.

2. A multiple function electromagnetic actuator, comprising: a plurality of solenoids each having a coil and an armature movable with respect thereto; a source of energizing current for said coils; means for selectively energizing said coils by connection to said source, less than all of the coils being energized at any time; and a structure of magnetic material adjacent said solenoids, providing a return path for the flux of each coil, said structure having a cross-sectional area normal to the flux of the coils, sufficient to accommodate the flux of the coils energized at any one time, without saturation, but less than that suflicient to accommodate the flux of all the coils if energized simultaneously.

3. The eletromagnetic actuator of claim 2 wherein said solenoids are aligned in side-by-side relation forming a solenoid assembly, and said structure of magnetic material includes a plate extending the length of the assembly, the cross-section of said plate adjacent one solenoid being less than that sufficient to accommodate the flux of one coil.

4. The electromagnetic actuator of claim 3 wherein said structure is a four-sided housing with each side comprising a plate extending the length of the assembly.

5. The electromagnetic actuator of claim 4 wherein said housing has ends forming a box with said four sides.

6. The electromagnetic actuator of claim 5 wherein said coils are potted in said box with an insulating material.

7. The electromagnetic actuator of claim 2 in combination with push button mechanism, each solenoid armature being connected with a push rod of said mechanism.

8. The electromagnetic push button actuator of claim 7 wherein each solenoid armature is aligned with the push rod to which it is connected.

9. The electromagnetic actuator of claim 2 in which each armature is movable into an opening through the associated coil and the structure of magnetic materials includes a plate extending the length of the solenoid assembly, said plate having openings therein aligned with the opening in each coil.

10. The electromagnetic actuator of claim 9 wherein said plate is on the side of the coils toward which the armatures move on energization of the associated coil.

References Cited UNITED STATES PATENTS 2,312,902 3/1943 Hickman et a1. 335l62 XR 3,185,909 5/1965 Jahn 317-155.5 XR 3,223,926 12/1965 Maugans 33410 XR 3,275,964 9/1966 Kumm 335-268 XR 3,389,355 6/1968 Schroeder 335268 XR JOHN F. COUCH, Primary Examiner W. M. SHOOP, 1a., Assistant Examiner U.S. Cl. X.R. 

